The present invention relates to novel polysilamethylenosilane polymers having polysilane-polycarbosilane skeleton, as represented by formula (III), to their production from selected chlorosilaalkanes as represented by formula (I) or a mixture of the chlorosilaalkanes and organochlorosilanes such as dimethyldichlorosilane and organotrichlorosilanes as represented by formula (II), and to their use in the production of silicon carbide: ##STR1## wherein, R.sup.1 represents methyl or chlorine atom, ##STR2## wherein, R.sup.2 represents alkyl group containing from 1 to 18 carbon atoms, allyl, vinyl, phenyl, trimethylsilylmethyl groups, ##STR3## wherein, R.sup.1 represents CH.sub.3 when R.sup.1 in formula (I) is methyl, while R.sup.1 represents Si-Si bond when R.sup.1 in formula (I) is Cl; R.sup.2 is alkyl group containing from 1 to 18 carbon atoms, aryl group, vinyl, phenyl, trimethylsilylmethyl groups and x, y, z are arbitrary constants.
The polysilamethylenosilane polymers can be prepared in one-step reaction from mixtures of chlorosilaalkanes and organochlorosilanes with alkali metal in one of appropriate solvents or in combination of solvents thereof. The solvents for dechlorination reaction can be toluene, xylene, benzene, tetrahydrofuran or mixture of solvents thereof. Toluene is the most preferable solvent and 80 to 20 mixture of toluene and tetrahydrofuran is most preferable as mixed solvent. Lithium, sodium, potassium or alloy of sodium and potassium can be used as the alkali metal for dechlorination. Such polysilamethylenosilane polymers are soluble and thermoplastic, and can be pyrolyzed to obtain improved yields of silicon carbide at atmospheric pressure.